PID Controller With
Feed Forward Compensation

PID Controller with
Feed Forward Compensation

This PID controller module is designed to provide all of the functions required to implement a complete high performance, closed loop, three mode (proportional, integral and derivative (PID)) control system on a single circuit board. In addition to the standard PID functions, the board contains feed forward as well as external bias and signal scaling circuits. All of the function blocks feature compatible signal levels, thus allowing them to be directly interconnected to produce the configuration required for a specific application. The module operates directly from the AC power line or from a unregulated, bipolar, DC power supply.

The board includes a transducer power supply, providing regulated positive and negative DC output, as well as PID amplifier section with independently adjustable gain, integration rate and derivative controls. Any combination of the proportional, integral and derivative functions can be selected by the board mounted jumpers. Each gain block function can be set independent of the others, the three signals are combined at the output with the bias and feed forward signals to produce to final signal to the process control element. The integration section can be clamped to prevent integral windup and the resulting loss of process control.

The feed forward compensation section is used to provide the fastest possible response to dynamic changes in the input signal. The feed forward signal is summed with the PID signal at the output and will not effect the static PID tuning.

Two separate signal scaling amplifiers are available, each with adjustable gain and bias. These amplifiers can be used to convert voltage or 4 to 20 ma. current input signals to levels that are suitable for additional processing by the other functions on the PID controller module. The signal scaling amplifiers provide inverted or non inverted outputs.

The difference amplifier section provides an output that is the result of subtraction of one input signal from another. This section can also be used as a inverting or non-inverting buffer with a gain of one. Optionally, this amplifier can be supplied with fixed gains of 5 or 10. These higher gains allow the difference amplifier to act as the summing input for load cells arranged in a full bridge configuration.

The PID controller module is supplied as a single, industrial grade, circuit board assembly. All external power and signal wiring connections to the board are made to plug in terminal blocks. All of the external connections to the terminal blocks as well as the adjustment controls are clearly marked on the board. The board can be mounted in the user's control enclosure on standoffs or located in plastic mounting track.

Applications: Signal conditioning and scaling with three mode PID control for speed, flow, pressure, position, temperature and tension control systems.